Response of ferroelectric nanodomain to alternative-current electric fields in morphotropic-phase boundary Pb(Mg_1/3Nb_2/3)O₃−PbTiO₃

The single crystal of morphotropic-phase-boundary (MPB) Pb(Mg_1/3Nb_2/3)O₃−PbTiO₃ (PMN-PT) is widely utilized in ultrasonic medical imaging devices due to its excellent piezoelectric properties. In recent years, alternating-current (AC) poling has proven effective in enhancing these properties, though AC poling beyond optimal cycles can lead to deterioration. In this study, to gain deeper insights into the mechanisms driving the change of piezoelectricity, the response of ferroelectric domains in an MPB PMN–PT single crystal was examined using in situ AC field electrical biasing transmission electron microscopy. The ferroelectric domain structure was significantly altered by applying a single cycle of an AC electric field at 12 kV/cm peak-to-peak and 20 Hz. Subsequently, with increased AC field duration, both a reduction in domain wall density and the generation of vertical microdomain bands were observed. These phenomena could, respectively, enhance and degrade the piezoelectricity of the material.